Long-Term Changes in Cognition Among Patients With Schizophrenia Spectrum Disorders and Different Durations of Illness: A Meta-Analysis

Objective: 

In this meta-analysis, we evaluated changes in cognition for patients with schizophrenia spectrum disorders (SSD) with different durations of illness (DOIs). 

Data Sources:

Records were identified through searches in PubMed, PsycINFO, CINAHL, and Cochrane until December 2021. We used terms related to SSDs, chronicity, course, and recovery. Study Selection and Data Extraction: We included 57 longitudinal studies, with a follow-up length of at least 1 year, investigating changes in 10 domains of cognition of patients who are all diagnosed with SSD. Changes in cognition were analyzed through effect sizes of change between baseline and follow-up assessments within each study. These changes were evaluated in different subgroups of studies including patients with a DOI <5 years, 5-10 years, or >10 years. We also investigated the influence of 19 potential moderators on these changes in cognition. 

Results: 

We found marginal improvements in overall cognition (d =0.13), small improvements in verbal memory (d = 0.21), processing speed (d = 0.32), marginal improvements in visual memory (d = 0.17), executive functioning (d = 0.19), and language skills (d = 0.13), and no significant improvements in the other cognitive domains. The largest improvements were achieved for patients with a DOI <10 years. Changes are more favorable for patients with a younger age, no schizophrenia diagnosis, female gender, higher education level, and low negative symptom severity. 

Conclusions: 

We observed only modest cognitive improvement in SSD almost exclusively in patients with early psychosis. Future research should focus on optimizing interventions targeting cognition in specific subgroups and the interrelationships with other life domains.